1. Field of the Invention
The present invention relates to a flat display apparatus using AC plasma discharge display.
2. Description of the Related Art
For example, Japanese Patent Laid-Open No. Hei 7-220641 has disclosed a flat display apparatus utilizing plasma discharge.
An example of a conventional flat display apparatus, for instance, as shown in FIG. 8 of a schematic perspective view with a partially cut away, and FIG. 9, of a schematic exploded perspective view, is composed of a flat vessel in which first and second substrates 101 and 102 for example, formed of a glass substrate are opposed to each other with a predetermined space held therebetween and the surroundings are sealed with airtightness.
A discharge maintaining electrode group 105 is provided on the internal surface of the first substrate 101, in which plural pairs of discharge maintaining electrodes 103 and 104 are formed of transparent conductive layers making a pair, for example, and are arranged in parallel.
The discharge maintaining electrodes 103 and 104 formed of the transparent conductive layers have high resistivities. Therefore, so-called bus electrodes 103b and 104b formed of metal layers having high conductivities are formed along the side edges opposed to the opposed sides of the pair of electrodes 103 and 104.
Partition walls 106 extended in a direction orthogonal to a direction of extension of the discharge maintaining electrodes 103 and 104 are provided with a predetermined space in parallel and a stripe-shaped address electrode 107 is formed between the partition walls 106 on the internal surface of the second substrate 102. Similarly, phosphors R. G and B having colors for emitting red, green and blue colors, for example, are coated by excitation through vacuum ultraviolet rays generated by plasma discharge between the partition walls 106.
A predetermined discharge starting voltage is applied between a selected address electrode 107 and one of the pair of discharge maintaining electrodes, for example, the electrode 103 so that the discharge is started in a portion where they cross. A predetermined AC voltage is applied between the electrode 103 and the discharge maintaining electrode 104 making a pair therewith so that the discharge in this portion is maintained. Through the vacuum ultraviolet rays generated by the discharge, light is emitted from the phosphor positioned in the cross portion and light emission display to be intended is carried out.
In such a conventional flat display device using general plasma discharge display, it is presupposed that both the discharge start and the discharge maintenance are carried out though negative glow discharge. For this reason, a space between the address electrode and the discharge maintaining electrode and a space between the pair of discharge maintaining electrodes are selected to be 100 xcexcms or more, for example, 130 xcexcms to 300 xcexcms which is a space between the electrodes for the generation of the negative glow discharge.
In the flat display apparatus of this type, recently, an enhancement in the density and definition of pixels has been required increasingly.
In order to obtain such an increase in the density and definition, it has been required that the pitch of the pair of discharge maintaining electrodes should be reduced.
In the conventional flat display apparatus using the negative glow discharge, however, if the space between the pair of discharge maintaining electrodes for carrying out discharge is reduced to 100 xcexcm or less, the discharge is not fully carried out so that the efficiency of generation of the ultraviolet rays is decreased. Consequently, the excitation of phosphors becomes insufficient so that a brightness is reduced. Therefore, the space between the pair of discharge electrodes is selected to be at least 100 xcexcms or more in the conventional general flat display apparatus. Correspondingly, the pitch between the pair of discharge maintaining electrodes is at least two hundreds and several tens xcexcms. For this reason, there is a problem that an increase in the density and definition cannot be fully obtained.
The present invention has an object to enhance high definition and high density display in a flat display apparatus, and furthermore, to reduce driving power, that is, consumed power.
The present invention provides a flat display apparatus in which first and second substrates are positioned opposite to each other, the first substrate is provided with a discharge maintaining electrode group having a plurality of discharge maintaining electrodes arranged thereon and the second substrate is provided with an address electrode group having a plurality of address electrodes arranged thereon. The discharge display is carried out in a discharging manner through ordinary negative glow discharge and mainly through cathode glow discharge.
In the present invention, thus, the negative flow discharge and the cathode glow discharge are combined for the discharging manner. Consequently, respective characteristics can be utilized.
More specifically, the pitch of the pair of discharge maintaining electrodes in the discharge maintaining electrode group can be reduced, that is, to be less than 50 xcexcms, preferably 20 xcexcms or less which is much smaller than 100 xcexcms. Thus, it is possible to fully increase the density and definition of pixels.
Referring to the discharge maintaining electrode group 105 having such a structure that the conventional discharge maintenance is carried out by the negative glow discharge, FIG. 10A is a schematic plan view showing a part thereof (illustrating only two pairs of discharge maintaining electrodes 103 and 104) and FIG. 10B is a sectional view taken along the line Bxe2x80x94B shown in FIG. 10A, in which the discharge maintaining electrodes 103 and 104 formed of a band-shaped transparent conductive layer are arranged with a space D of 100 xcexcms or more, for example, approximately 130 to 300 xcexcms as described above. A space Dc between an adjacent pair of discharge maintaining electrodes should be minimum. Therefore, even if a width W of each of the discharge maintaining electrodes 103 and 104 is selected to be small, for example, approximately 30 to 40 xcexcms, a pitch P of each set of discharge maintaining electrodes should be set to at least two hundreds and several tens xcexcms, thereby obstructing an increase in the density and definition of displayed pixels.
On the other hand, as described above, in the case that the discharge maintenance is carried out by the cathode glow discharge, the space between the pair of discharge maintaining electrodes can be reduced to 20 xcexcms or less. Consequently, the pitch of each pair of discharge maintaining electrodes can fully be reduced.
According to the present invention, moreover, the driving power can be considerably reduced by using the cathode glow discharge as compared with the case of the negative glow discharge. In particular, great power saving effects can be obtained by the driving power in large screen display.
Alternatively, brighter display can be obtained with the same consumed power.